In a gas turbine engine, hot gas are routed from a combustor to a turbine section, in which stator vanes are designed to direct hot combustion gases onto rotor blades resulting in a rotational movement of a rotor to which the rotor blades are connected. Radially inwards and outwards of aerofoils of these stator vanes and rotor blades, platforms, a casing, or other components may be present such as to form an annular fluid passage into which the aerofoils of the stator vanes and the rotor blades extend and through which hot combustion gases are led.
As rotating parts—rows of rotor blades—and non-rotating part—rows of stator vanes—are arranged alternately, gaps may be present between the rows of rotor blades and the rows of stator vanes. It is a goal to reduce the size of the gaps and/or to seal these gaps such that no or little of the mainstream fluid is lost via these gaps. The structure to seal these gaps between rotor blades and stator vanes may be called rim seal.
Patents and patent applications EP 1 731 717 A2, EP 1 731 718 A2, EP 1 939 397 A2, U.S. Pat. No. 7,452,182 B2, and US 2008/0145216 A1 show different kind of seals, that will keep the hot mainstream fluid within the annular fluid passage, possibly without leakage of hot fluid into the cavities of the rim seal and possibly also without egress of cooling fluid via the rim seal into the mainstream. A small gap may be present between the stator vanes and the rotor blades through which, also depending on tolerances, heat expansion of turbine parts and pressure differences of the involved fluids, the mainstream fluid may leak through the seal leaving the mainstream fluid path. It may also happen that a second source of fluid—possibly air provided anyhow for cooling the rotor blades—may leak through the seal in the opposite direction entering the mainstream fluid path. Both types of ingress or egress of fluid and/or air may even happen at different modes of operation for the same seal or may even happen at different circumferential positions in the mainstream fluid path.
Thus, it is a goal of the invention to provide a modified turbine arrangement that results in minimal ingress and egress of fluid via the seal to/from the mainstream fluid path in most modes of operation, e.g. resulting in less aerodynamic losses and a higher efficiency of the turbine arrangement. Particularly it may also be a goal to provide a turbine arrangement such that less sealing air is required during operation.